STUDY OF BIOCATALITIC REACTIONS INVOLVING FUNCTIONAL MICROORGANISMS WITH METAL OXIDES: AN ALTERNATIVE FOR GLYCEROL VALORIZATION

Biomaterials, bio-hybrids, metal oxide of transition, biotransformation, filamentous fungi, glycerol.

The objective of this master's dissertation was to integrate particles of TiO2 (titanium oxide anatase) and WO3 (tungsten trioxid) in Aspergillus niger and Phialomyces macrosporus fungi’s cell walls and to study a production of organic acids by these biohybrid from the conversion of glycerol. Initially, the A. niger/TiO2, A. niger/WO3, P. macrosporus/TiO2 and P. macrosporus/WO3 bio-hybrids were grown in 50 mL of a solution containing BD and particles of TiO2 (0.40 g) and WO3 (0.58g) during four days. Then, it was added a solution containing 20 mL of glycerol and the system was kept in fermentation for more ten days. The resulting fermented broth containing glycerol, the BD medium and the bioconversion products passed by a process of extraction using a 2: 3 (v / v) extractive mixture of dichloromethane/ethyl acetate with 1% (v / v) of formic acid. Using a scanning electron microscopy (SEM), the bio-hybrids had their morphology studied to verify the characteristics of the material after the fermentation period. A chromatography method utilyzing the high efficiency liquid chromatography (HPLC) coupled to diode (DAD) and refractive index (IR) chromatography was optimized for the analysis of fermented broth samples in which the chromatography conditions employed were the use of a Lichrospher® C18 (4.6 x 250 mm, 5 μm) column from Agilent (Germany), mobile phase composition of 2% acetonitrile, 49% 0,1% phosphoric acid solution and 49% water, isocratic method, 6 mL.min-1, temperature column of 35°C, analysis time of 15 minutes and injection volume was 20 μL. The selected wave ‘s length was 210 nm. The optimized variables served as the basis for the development of an analytical method LC-ESI-IT, whose chromatographic conditions were the use of a Kromasil C18 (4.6 mm x 250 mm, 5 μm) chromatographic column as composition of the mobile phase the solvent A = H2O and phomic acid (0,1% v / v), solvent B = acetonitrile. The elution gradient started isocratic for 13 min with 5% B, after 14-24 min the concentration of 5-100% B was increased and in 25 min the concentration returned to 5% acetonitrile until the end of the 35 min analysis. The flow rate of the mobile phase used was 0.6 mL.min-1 and the injection volume was 20 μL. From a semi-quantitative analysis, the production of citric acid in appreciable amounts and lactic acid in small amounts (traces) by A. niger/TiO2 and P. macrosporus/TiO2 hybrids compared to native cultivated fungi in glycerol medium. The A. niger/TiO2 bio-hybrid produced a 3-fold higher amount of citric acid when grown in glycerol medium as compared to the native fungus.